test/jdk/java/util/Locale/SoftKeys.java

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/*
 * @test
 * @bug 8196869
 * @summary Make sure we deal with internal Key data being cleared properly
 * @ignore This test aims to provoke NPEs, but due to the need to constrain
 *         memory usage it fails intermittently with OOME on various systems
 *         with no way to ignore such failures.
 * @run main/othervm -Xms16m -Xmx16m -esa SoftKeys
 */
import java.util.*;

public class SoftKeys {

    public static void main(String[] args) {
        try {
            // With 4 characters in "language", we'll fill up a 16M heap quickly,
            // causing full GCs and SoftReference reclamation. Repeat at least two
            // times to verify no NPEs appear when looking up Locale's whose
            // softly referenced data in sun.util.locale.BaseLocale$Key might have
            // been cleared.
            for (int i = 0; i < 2; i++) {
                for (int j = 0; j < 512*1024; j++) {
                    Locale.of(HexFormat.of().toHexDigits((short)j));
                }
            }
        } catch (OutOfMemoryError e) {
            // Can happen on some system configurations, and while increasing heap
            // size would allow GC to keep up, it also makes it impractically hard
            // to reproduce NPE issues that could arise when references are being
            // cleared.

            // Do a System.gc() to not throw an OOME again in the jtreg wrapper.
            System.gc();
        }
    }
}